Oxetanocins are antibiotics which were recently found (U.S. Pat. No. 4,743,689): ##STR3## and are nucleosides showing anti-tumor and anti-viral activities which contain as sugar the oxetan ring in place of ribose.
Physiological activities of cyclobutane derivatives in which carbon has been substituted for oxygen in the oxetan ring of oxetanocin have attracted the present inventors' attention. The present invention is to provide a novel process for producing such cyclobutane derivatives as intermediates for synthesis.